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How renewables have changed

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How renewables have changed

By Nicholas Newman

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In little more than two decades, scientists and technologists have evolved a global, renewable-energy industry capitalizing on the free resources of wind and sun…

Global solar photovoltaic capacity has grown from around five gigawatts in 2005 to an approximately 306.5 gigawatts in 2016. This trend was accompanied by sharp drops in the price of photovoltaic panels. Global wind power also grew sharply from 4,117 MW in 2011 to 14,384 MW in 2016.

Solar power

The first solar cells were developed in 1876 by William Adams and his student Richard Day, from their discovery that selenium, when exposed to light, produced electricity. The principle that light could be converted into electricity without heat or moving parts was recognized by the German industrialist, Werner von Siemens, as “scientifically of the most far-reaching importance.” Four decades later, in 1918, Polish scientist Jan Czochralski developed a way to grow single-crystal silicon and in 1921, Albert Einstein won the Nobel Prize for explaining the photoelectric effect.

The groundwork for the modern solar power industry was laid in 1953 by Calvin Fuller, Gerald Pearson and Daryl Chapin who jointly invented the silicon solar cell which was sufficiently powerful to run small electrical gadgets. This discovery was reported by The New York Times as marking “the beginning of a new era, leading eventually to the realization of harnessing the almost limitless energy of the sun for the uses of civilization.” During the space race between Russia and the U.S. solar cells with an efficiency of barely 14 percent were used to power space-crafts and satellites. In the 1970s a series of discoveries made by a team from the oil major Exxon, laid the foundations for dramatic cost reductions in solar cell production to around $20 per Watt today and efficiency improvements up to reach 44.5 percent in 2017. Today there are utility-scale, grid-connected solar power stations. There is the solar thermal collector which uses thousands of parabolic mirrors to reflect the sun’s energy onto a focal point. The energy is used to heat water to produce steam which in turn powers a steam turbine to create electricity. There is also utility-scale solar photovoltaic technology, which converts energy from sunlight directly into electricity using large arrays of solar panels which are in turn made up of solar cells. Photovoltaic technology has produced both the crystalline silicon solar cell (which has 85-90 percent market share) and thin films of semi-conducting material. The most visible sign of solar cells is to be found on residential rooftops as the price of a standard 6 kW home solar system in the U.S. has fallen from $52,920 to just $18,840 in the past decade. Other practical uses of solar cells include solar tiles or bricks, solar windows and even solar car ports. There are also experimental solar powered cars and aircrafts. Continuous development of higher efficiency solar cells, economies of scale and benefits of experience have combined to make solar power commercially viable.

Wind power

The first wind turbine to generate electricity was invented by James Blyth an engineer at Strathclyde University in 1887. Subsequent incremental improvements were incorporated in 2000 Danish windmills, said to produce over 30MW of power at the start of the 20th century. Around the world, farms in remote locations began to use wind power to meet their own needs, but for large-scale use the technology was not commercially viable.

Workers at a repowering site in northern Germany (BWE, Tim Riediger)

The first large-scale grid-connected commercial MW sized turbine was installed in Vermont (USA) in 1941. Over three decades later, in 1975, NASA appointed Louis Divone, to lead research into utility-scale wind turbines at its Glenn Research Center. The team of experts from General Electric, Westinghouse, United Technologies and Boeing found that two blades were just as effective as three blades and yielded substantial cost savings and blade weight reductions. Subsequently, various improvements were made by various technologists to the blade rotors reduced wear and tear of the gear box and added flexibility minimized the transfer of the bending loads in the drivetrain.
Capitalizing on the U.S. research, Vestas produced its first commercial wind turbine in 1978. By 1991 it sold its 1000th wind turbine. By 1980, other leading electrical engineering companies start to become involved in wind technology including, General Electric and Siemens, leading to a reduction in wind power price to $0.38/kWh in the United States.
The United States, Britain, Denmark and Germany encouraged wind-power through subsidies and tax incentives in efforts to reduce emissions. In 1995, Vestas built the equipment for the first offshorecommercial wind farm located near Vindeby, in the southern part of Denmark. The wind farm consists of eleven 450 kW turbines. By 2017 reached 539,291 MW, according to preliminary statistics published by WWEA in 2018, and it was not surprising to see, even in the remotest parts of the world, wind turbines both off and onshore. Then reliability was around 70 percent which with incremental improvements is around 98 percent today.

The first commercial offshore floating wind farm equipped with a Siemens turbine established in the North Sea off Scotland

In 2017, the first commercial offshore floating wind farm equipped with a Siemens turbine was established in the North Sea off Scotland to power 20,000 households, according to Statoil. In recent years projects have become bigger, smarter, more reliable and productive, enabling many projects to be built without the need for direct subsidies.
Current turbines, averaging 4.1 MW with a hub height of 90 meters, will soon be replaced by 11-megawatt colossuses with hubs 125 meters off sea level and blades spanning 190 meters.

Timeline of average Enercon wind turbine sizes (Jahobr, wikimedia)

In sum, the falling cost of wind, solar and the arrival of competitive energy storage, is turning renewables into a sound commercial investment.

Technology

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